The present invention relates to a method of and an apparatus for separating fibers from a fibrous sliver and supplying them in this condition to a twist forming element of an open-end spinning unit, the fibers being exposed to a sucked-in air flow in the fiber separating zone having a combing-out cylinder.
There are known apparatus for open-end spinning yarns from staple fibers, which apparatus are characterized by a substantially higher productivity than the well-known ring spinning machines. Such open-end spinning machines of the first generation have operated at a spinning rotor speed of about 30,000 rpm. The second generation of these machines has already achieved speeds within the range of from 45,000 to 60,000 rpm. Recently, in the development of machines having still higher productivity, that is, machine operable within the spinning rotor speed range of about 100,000 rpm, there have been encountered certain problems in the operation of fiber separating devices of the type installed in the prior art machines having the aforementioned lower operating speeds, so that these devices have to be further improved.
A higher machine productivity makes for larger fiber amounts to be processed per unit of time and to be supplied in the separated condition to the high-speed spinning rotor. To meet requirement, it is necessary, on the one hand, to increase the velocity of fiber flow to be supplied to the spinning rotor and, on the other hand, to raise the effect of the combing-out cylinder upon the fibers and to reduce the contamination of the inner space as well as sliver inlet spaces of the fiber separating device. Such contamination in the lower output machines is practically irrelevant.
In the well-known open-end spinning machines, fibers having left the combing-out cylinder zone are accelerated by air flowing through a fiber supply duct. Preferably, relatively short ducts are used for this purpose since long ducts lay excessive claims on the manufacture thereof and are also disadvantageous from the power economy viewpoint. However, with a relatively short duct, even at a relatively high air throughflow velocity, it is impossible to achieve, owing to a short passage, a substantial acceleration of the fiber flow if fibers are supplied at a low velocity. Experiments in this field have proven that an average velocity of fibers, when stripped from the combing-out cylinder clothing, is lower than the circumferential speed of said clothing. This can be attributed to the fact that all the fibers, after having been separated, are not entrained by the active elements of the combing-out cylinder, but are, on the one hand, airborne through the interspace between the surface of the cylinder and the wall of the cavity receiving said cylinder, and, on the other hand, are braked or retarded by the contact with said wall. In the well-known open-end spinning machine constructions, the sliver inlet zone and the fiber separating zone are hermetically sealed off to prevent dust and other impurities from entering the spinning unit from the ambient atmosphere. This feature prevents, however, an air amount sufficient for conveying fibers through the combing-out cylinder region from being sucked in. If one considers that increased machine productivity is brought about by an ever increasing effect of the combing-out cylinder upon the fibers which causes the amount of fibers together with undesirable admixtures conveyed around the combing-out cylinder to increase, it becomes clear why those regions are insufficiently scavenged by air and thus get clogged.
To eliminate the aforedescribed disadvantage, various measures have been attempted to enable air to be supplied in limited amounts into various regions of the cavity accommodating the combing-out cylinder. However, such measures have proven rather complicated from the constructional viewpoint and, apart from that, are not completely efficient if used in highly productive open-end spinning machines. Moreover, in a construction having a cover above the feed roller, the roller front portion is fouled with dust and fiber fly in the form of stuffed clots which are densified, owing to the contact between the front of the rotating feed roller and the stationary cover wall.
To improve the cleaning of extra short fibers from the device, there has been provided a construction wherein air is supplied through a small opening in the direction perpendicular to the front of the feed roller. However, such a measure is not satisfactory for a universal cleaning purpose and its effect is limited to a close proximity of the mouth of said opening.